When driving a vehicle, the driver visually checks a surrounding status of the vehicle. However, a blind spot sometimes arises where the driver cannot visually recognize due to the vehicle body of its own or existing obstacles. “Blind spot” means an area of which one cannot get a view from a certain angle. Here, it means an area of which the driver cannot get a view. “Vehicle of its own” means a vehicle that the driver is on. In order to assist the driver to recognize such a blind spot, a technology is proposed in which an image of the surroundings of vehicle is captured by a camera mounted on the vehicle body and the image is displayed on a screen of a display device installed in the vehicle. The followings are examples of such a technology.
A technology is described in Patent Document 1 in which, by using lateral cameras and a rear camera, images are cut out from the respective camera images, to be combined and displayed. An image cutting out range is changed depending on a vehicle speed. When the vehicle runs faster, lateral camera images are cut out in wider ranges. Thus, an area to be displayed as a combined image is broadened, so that blind spots can be decreased. “Lateral camera” means a camera for capturing images in the right side or left side of the vehicle. “Rear camera” means a camera for capturing images in the rear side of the vehicle. “Vehicle speed” means a speed of the vehicle.
A method is described in Patent Document 2 in which surrounding images of a vehicle captured by a plurality of cameras are combinedly displayed on a display device while each ratio of image displaying areas to a screen area of the display device is changed. By changing each displaying ratio depending on a status of steering wheel operation, a notable image can be highlighted from among a plurality of captured images displayed on a single screen.